This invention relates to a method of adding to a refractory lined vessel in a working environment at temperatures over 800.degree. F.
Vessels used to smelt or refine copper or nickel are lined with refractory linings capable of withstanding the temperatures and other wear forces such as thermal shock and/or mechanical erosion encountered in the smelting or refining process of the above metals.
Most common refractory linings used are linings with principal ingredients of Magnesite, Chrome and/or Alumina although Zirconia can also be used.
The principal vessels used in the refining of copper and/or nickel are known as convertors and Anode refining vessels. In addition, one type of vessel used in the smelting of metals is referred to in the industry as a reactor. These types of vessels all incorporate pipes through the refractory lining which are used to inject air and/or oxygen into the material being refined or smelted. Such pipes are commonly known as tuyeres.
The number of tuyeres varies widely depending on the particular use. For example, an anode refining vessel may have one to six tuyeres; a convertor may have 20 to 60 tuyeres and a reactor may have 40 to 80 tuyeres depending on the size of the vessel and the output capacity of the vessel.
The relatively cold gases are forced into the material being refined or smelted and react with the material to generate substantial heat. In addition, turbulence is created in this area by the pressure of adding the gases to the molten charge. Such charges are subjected to this blowing of gases into them through the tuyeres until they have reached the acceptable stage of refinement or smelting for the material They are then transferred from that vessel to the next stage of the process.
The extreme conditions encountered by the refractory lining in the area of the tuyere pipes causes the refractories and the pipe lining to wear back at a rate exceeding the wear in other parts of the vessel. Such wear differentials may be exaggerated further in anode refining vessels and/or convertors due to the emptying of the vessel of completed charges and the filling of the vessel of charges to be treated. This creates wide temperature fluctuations at the tuyere line since it is necessary to blow relatively cold gases through them to keep the liquid charge from blocking them. Such temperature fluctuations can accelerate the wear of the refractory through thermal shock caused by the temperature fluctuations.
As previously stated, these and other forces cause the refractories to wear at an accelerated rate as compared to other parts of the vessel. When the tuyere area is worn to a thickness considered unsafe for further use, it is common to cool down the vessel, remove the worn area and replace it.
Such large furnaces with refractory linings usually from 12" to 24" thick take several days to cool down to ambient temperatures from their working temperatures. In addition, then the repair must be made and the vessel must be reheated over two or three days to prevent damage to the refractory lining by too rapid heating. In addition, the rest of the lining which is still acceptable for use is damaged by the thermal shock of cooling it down and reheating it, thus shortening its life.
Accordingly, it is very advantageous to be able to repair refractories in the tuyere area while the vessel is still hot. However, the most common practice is to run the vessel until the tuyere line has reached the limits of its life and then cool the vessel down to ambient temperatures to repair it.
One of the difficulties encountered in repairing the tuyere area is that when the refractory lining wears the tuyere pipe wears back also. It is time consuming and expensive to replace the tuyere pipe and if it is not replaced, the repair refractories are subjected to direct contact with the gas stream, unprotected by the tuyere pipe. In addition, each tuyere is rammed open with a rod between each charge to ensure that the charge has not blocked the tuyere. This subjects the surrounding unprotected repair refractories to such stresses that most copper or nickel producers would expect the refractories to fail too quickly to substantially extend the life of the tuyere line refractories.
Hot repairs have been attempted in the past by gunning wet refractories into the tuyere line area and using a pipe or rod inserted inside the tuyere pipe to prevent the gunning material blocking the tuyere pipe hole. This method is generally considered ineffective as a repair method to substantially extend the life of tuyere line refractories for the reasons outlined in the preceding paragraph.